How do I know if I have a "bad copy"

With my limited knowledge of lenses and slr cameras, I do not know how to determine if I have a "bad copy" of a lens. I keep reading here that some people have bad copies. Is there a definitive test I can perform so I will know for sure how good my lens is. I am talking about my 17-70. I have seen some amazingly sharp shots here on this forum with this lens. So far, I don't feel like I have taken a picture as sharp as some I have seen. I am not saying they are blurry or OOF, but just not crisp. I need to know if it's me or the lens. What should I do?

Stefan

There are a myraid of lens tests, but there is a much better way. Go take some pictures and see how they come out.

If you absolutely must do a lens test, the "battery" test is easy. Line up 5 batteries at a 45 degree angle, spread out about 6 inches apart. Focus on the center one, and take some pictures. If you really want to get particular use a tripod, mirror lockup, and timer. Review the photos. Check to see that the battery you focused on is the most in focus and check the writing to see if it looks "sharp" to you.

I honestly believe that user error is far more common than "bad" lenses.

Stefan A wrote in post #2151907
With my limited knowledge of lenses and slr cameras, I do not know how to determine if I have a "bad copy" of a lens. I keep reading here that some people have bad copies. Is there a definitive test I can perform so I will know for sure how good my lens is. I am talking about my 17-70. I have seen some amazingly sharp shots here on this forum with this lens. So far, I don't feel like I have taken a picture as sharp as some I have seen. I am not saying they are blurry or OOF, but just not crisp. I need to know if it's me or the lens. What should I do?

Stefan

how experienced are you with your equipment?

do you have lenses that you are satisfied with?

the best test is to go out and take many pictures at various f-stops and focal lengths. review them on your computer.

if you have pictures you are unsure about post them here with exif and let the experts weigh in.

if you are unhappy with the results send your lens in for calibration or get a replacement.

don't make yourself crazy shooting batteries and newspapers because if you don't know exactly what you are doing those are the worst kinds of tests.

ed rader

OK - here a a couple examples. The 2nd one was on a tripod and the 1st handheld. Exif attached.

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those look good to me!

ed rader

Maybe add some contrast in PP. Always does wonders for my DSLR shots.

Every Sigma 17-70 I try was litle soft on ~17-20mm and one was also soft on 60-70mm . Try shooting few pictures on 17, 25, 35, 50 and 70mm and compare. Your samle photos seems to be ok.

They look OK to me at that size, did you apply any sharpening? - The main thing is are you happy?

I did a little unsharp mask on both. The first one I think is OK. But the 2nd seems fuzzy to me.

Stefan

I agree with what Ed said.

And beautiful pictures! I wouldn't complain about those.

If i compare my 35L with my ancient 35-70 kit lens "from the 1000fn" i cannot tell any sharpness issue when looking at a pic of that size, unless the lens is a real dog you won't, these differences are only really amazing when compared by a 100% crop of each image.

Did you check the EF Lens FAQ/Sticky thread?